My frogspawn started out as a single-headed frag with the diameter of about a nickel....

...and is currently a fist-sized multi-headed colony in about a year and a half. New heads have developed from both budding and polyp development along the main tissue-covered branches:

Additionally, if the living tissue at the base of the skeleton is in direct contact with live rock, skeletal growth and coral tissue can encrust the adjacent rock and result in additional heads sprouting from the new encrustment rather than from the main skeletal structure: